Question

Commercial sodium hydroxide weighing 30 g has some sodium chloride in it. The mixture on dissolving in water and subsequent treatment with excess silver nitrate solution formed a precipitate weighing 14.3 g. What is the percentage of sodium chloride in the commercial sample of sodium hydroxide? The equation for the reaction is

\[\ce{NaCl + AgNO3 -> AgCl + NaNO3}\]

[Relative molecular mass of NaCl = 58, AgCI = 143]

Answer 1

\[\ce{\underset{58}{NaCl} + AgNO3 -> \underset{143}{AgCl} + NaNO3}\]

As 143g of AgCl is obtained from 58 g of NaCl

1 g of AgCl is obtained from `58/143` of NaCl

∴ 14.3 g of AgCI will be obtained from = `58/143 xx 14.3`

= 5.8 g of NaCl

Weight of commercial NaOH = 30 g

Percentage of NaCl in NaOH = `5.8/30 xx 100`

= 19.33%